Validating short-term atmospheric processes that impact forecasts of sea-ice melt-back and freeze-up in coupled limited area model simulations of the marginal ice zone

Amy Solomon

Abstract
The dramatic decrease of Arctic sea-ice has led to a new Arctic sea-ice paradigm and to increased commercial activity in the Arctic Ocean. NOAA’s mission to provide accurate and timely sea-ice forecasts, as explicitly outlined in the National Ocean Policy and the U.S. National Strategy for the Arctic Region, needs significant improvement across a range of time scales to improve safety for human activity. Unfortunately, the sea-ice evolution in the new Arctic involves the interaction of numerous physical processes in the atmosphere, ice, and ocean, some of which are not yet understood. These include atmospheric forcing of sea-ice movement through stress and stress deformation; atmospheric forcing of sea-ice melt and formation through energy fluxes; and ocean forcing of the atmosphere through new regions of seasonal heat release. Many of these interactions involve emerging complex processes that first need to be understood and then incorporated into forecast models in order to realize the goal of useful sea-ice forecasting. I will present results from a study that uses observations collected in recent Arctic field programs to validate the simulation of these processes in limited area coupled forecast models. For example, data from the recent 2014 Arctic Clouds in Summer Experiment (ACSE) is being used to validate the surface energy budget, ocean mixing, and cloud structure during the summer ice-edge retreat and onset of the fall freeze-up in the emerging marginal ice zone (MIZ) of the Laptev, East Siberian, and Chukchi Seas. The limited area coupled forecast model used for this study is a modified version of the Regional Arctic System Model, which includes the Weather Research and Forecasting (WRF) atmospheric model, the LANL Parallel Ocean Program (POP) and Community Ice Model (CICE) and the Variable Infiltration Capacity (VIC) land hydrology model. The model has been configured to study MIZ-local atmospheric processes, such as lower-level jets, and how they impact sea-ice evolution and ocean mixing. The underlying hypothesis for this study is that errors in simulations of short-term atmospheric processes significantly impact the forecast of seasonal sea-ice retreat in summer and its advance in autumn in the MIZ. We therefore focus on validating short-term (0-20 day) ice-floe movement, the autumn freeze-up processes in the near-ice open water and MIZ, and the role of storms in modulating stress and heat fluxes.